Thesis (M.S.)--The Chinese University of Hong Kong. / Bibliography: leaves 68-71. / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter CHAPTER 2 --- PRINCIPLE OF NORMAL COORDINATE ANALYSIS --- p.5 / Chapter CHAPTER 3 --- THE UREY-BRADLEY FORCE FIELDS OF HEXAHALIDE IONS OF NIOBIUM AND TANTALUM --- p.20 / Chapter CHAPTER 4 --- THE UREY-BRADLEY FORCE FIELDS OF PERHALYL FLUORIDE --- p.34 / Chapter CHAPTER 5 --- THE UREY-BRADLEY FORCE FIELDS OF ISOTOPIC CHLORYL FLUORIDES --- p.47 / Chapter CHAPTER 6 --- CONCLUSION --- p.66 / BIBLIOGRAPHY --- p.68 / APPENDIX --- p.72

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Inaug.-diss.--Bonn. / Lebenslauf. "Bibliographie": p. [100]-102.

Flash photolysis of AH₃ (where A = P, As or Sb) produces metastable A atoms in the ²D° and ²P° states, AH, AH₂ and A₂. Similar transients were also observed from ACl₃ with the exception of Sb₂ from SbCl₃. The reaction forming A₂ is probably: 2AH(2ACl) + A₂ + H₂(Cl₂) Since this reaction is endothermic for SbCl no Sb₂ is observed following photolysis of SbCl₃. From the photolysis of PCl₃ a new spectrum was observed and attributed to PCI (³π ← ³Σ⁻). The bands resulting from this transition each consist of three subbands which are easily recognized since the spin-orbit splitting is less than the vibrational spacings in the ³π state. The ΔG₁/₂ value for the ³Σ⁻ ground state is significantly larger than that reported by Basco and Yee⁽¹⁶⁾ from a long wavelength spectrum assigned to PCI. This system may arise by absorption from the metastable ¹Δ state which has the same electronic configuration as the ground state. Spectra of the mixed Group V diatomics AsP, PSb and AsSb were obtained by flashing corresponding mixtures of AH₃ plus BH₃ They are formed by: AH + BH → AB + H₂ AsP was also formed from the mixture of AsCl₃ and PCl₃. That neither PSb nor AsSb were produced from the corresponding chlorides is due to the probable endothermicity for the reaction. The spectrum of AsP consists of a number of strong red degraded bands between 2030 Å and 2260 Å. Due to perturbations a vibrational analysis was not possible. A system of bands in the region of 3000 Å to 3225 Å attributed to AsP by Yee and Joness⁽²⁶⁾ was not detected. Two systems of red degraded bands are attributed to PSb. System 1 (3740 Å -3690 Å) has also been observed by Yee, Jones and Kopp⁽²⁷⁾. System 2 (2420 Å - 2640 Å) is much stronger than system 1. Again, as for AsP, strong perturbations prevented a vibrational analysis. A group of red degraded bands in the region of 3710 Å to 3525 Å were attributed to AsSb. This spectrum was also observed by Yee and Jones⁽²⁸⁾. A vibrational analysis gave ωe and ωexe values of 274.3 cm⁻¹ and 1.7 cm⁻¹ for the upper state. / Science, Faculty of / Chemistry, Department of / Graduate

Several electronic transitions of NO₂, SO₂, and CS₂ have been photographed, and the rotational structures of some of the bands have been analysed. In the spectrum of CS₂, large numbers of 'hot' bands in the first electronic absorption systems of ¹²CS₂ and ¹³CS₂ (3400-4100 A) have been analysed from high-dispersion plates, and accurate rotational constants have been obtained for the overtones of the ground state bending vibration up to v₂ = 6 and ℓ = 3 for ¹²CS₂ and v₂= 4, ℓ = 2 for ¹³CS₂. The energy differences between the various levels with the same ℓ value have been determined to an accuracy of about ±0.006 cm⁻¹ but (because of the parallel polarization of the electronic transition) the absolute energies of levels with ℓ > 0 could not be obtained from these spectra. A detailed rotational analysis of the (0,0) band of the 2²B₂- X²A₁ electronic transition of N0₂, at 2491 A, has been carried out. Although the lines are broadened as a result of predissociation, it has been possible to determine the five quartic centrifugal distortion constants and the spin-rotation coupling constant εaa for the upper ν₃' state. The centrifugal distortion constants allow the position of the unseen vibrational level ν₃' to be estimated : the results offer no support to the suggestion of Coon, Cesani and Huberman that there is a double minimum potential function in the antisymmetric stretching coordinate of the ²B₂ state. The geometrical structure of the zero-poi level of the ²B₂ state is r(N - 0) = 1.314₂ A, ∠0N0 = 120.8₇°, and its lifetime (as calculated from the linewidths) is 42 ± 5 picoseconds. About 160 rotational lines in the region 7370 - 7410 A in the electronic spectrum of NO₂ have been assigned. The lines form the K = 0, 1, and 2 sub-bands of a perturbed parallel band where the upper state A constant is about 17 cm⁻¹. In a diabatic representation, the band can be considered to be a transition within the ground state manifold, which obtains its intensity by vibrational momentum coupling from a nearby band of the A²B₂-X²A₁ electronic transition; its d assignment is 2 13 1-000. Comparison with the spectrum of ¹⁵N0₂ shows that the nearby A₂B₂ level has quite a small amount of vibrational energy, which is not inconsistent with the assignment by Brand, Chan, and Hardwick that the (0,0) band of the A - X transition is at 8350 A. The implications of the electron spin-rotation parameters and the intensity of the 7390 A band are discussed. Rotational analyses have been carried out for the (0,0) bands of the ã³B₁-X¹A₁ absorption systems of S¹⁶0₂ and S¹⁸0₂, from high dispersion plates taken with the gases at dry ice temperature. The rotational analysis of the (0,0) band of S¹⁶0₂ given by Brand, Jones and di Lauro is confirmed in-general, but their values for the anisotropic spin fine structure constants are found to be in error. Our new values remove the discrepancy in the sign of the spin-spin interaction parameter β=E between the gas phase work and the solid state value given by Tinti. This discrepancy had been rationalized by Brand, Jones and Di Lauro in terms of a different choice of phases for the angular momentum operators, but this argument is shown to be incorrect. The spectrum of S¹⁸0₂ confirms our new values for the spin constants in detail. The C¹B₂-X¹A₁ absorption spectra of S¹⁶0₂ and S¹⁸0₂ between 2350 and 2270 A have been analysed in detail from high dispersion plates taken with the gases at dry ice temperature. The centrifugal distortion constants for the (0,0) band are found to disagree with those reported by Brand, Chiu, Hoy and Bist; rotational constants for the other members of the ν₂' progression are given to high precision. Effective constants for the C¹B₂ state of S¹⁸0₂ are reported. Irregularities due to Coriolis coupling observed in the 002 levels of both isotopic species have' been deperturbed to giventhe rotational constants of the unseen 011 levels. A similar deperturbation of the levels 012 and 100 of S¹⁶0₂ has been used to give the rotational constants of the unseen 021 level of the C¹B₂ state. The spectroscopically determined Coriolis and anharmonic coupling constants are reported. An estimate of the energy of the unseen 001 level from the band origins observed gives 236 and 234 cm⁻¹ for S¹⁶0₂ and S¹⁸0₂, respectively. The large anharmonicity observed in the ν₃' manifold confirms the double minimum potential in Q₃ suggested by Brand, Chiu, Hoy and Bist, but indicates that the barrier height is smaller than the value of 100 cm⁻¹ that they report. A detailed theoretical analysis of the direct spin-orbit interaction between electronic states of the same spin multiplicity has been carried out. / Science, Faculty of / Chemistry, Department of / Graduate

Electron impact and electron spectroscopic techniques provide many useful tools for the examination of the physical structure of matter. One of these tools is electron energy loss spectroscopy (EELS). This thesis describes the application of EELS to studies of excitations of the inner-shell electrons of gaseous molecules. Preliminary, low resolution studies in the Department of Chemistry at UBC by G.B. Wight have demonstrated that the technique is experimentally feasible and that many interesting spectroscopic features occur in the inner-shell electron energy loss spectra (ISEELS) of molecules. The present work builds on this foundation and has provided significant extensions not only of the technique but also of its application. Improvements in the experimental apparatus have led to higher energy resolution and more flexible scanning arrangements. The molecular I SEE L spectra of several series of related molecules have been studied including investigations of all observable inner-shell excitation structure between 50 and 700 eV in the simplest saturated, unsaturated and aromatic hydrocarbons (CH₄, C₂H₆, C₂H₂, C₂H₂ and C₆H₆), the methyl halides (CH₃X, X = F, Cl, Br, I), the monohalobenzenes (C₆H₅X, X = F, Cl, Br, I), the chloromethanes (CHxCl₄-x, x = 0 to 4) and chloroethane. A number of specific investigations have been carried out in order to assist spectral interpretations and to further understand the physical nature of inner-shell excitation phenomena. Isotopic substitution has been used to aid the assignment of the carbon 1s spectra of CH₄ (CD₄) and CH₃Br (CD3Br). The first observation of the gas phase energy loss equivalent of extended X-ray absorption fine structure (EXAFS) is reported in the spectra of CH₂CI₂, CHCI₃ and CCI₄. Molecular electric quadrupole transitions have been identified in the sulphur 2p excitation spectrum of SF₆. The improved experimental resolution has led to observations of vibrational structure in the inner-shell excitation spectra of N₂, CO, C₂H₄ and the methyl halides. In addition to the ISEELS studies, electron-ion coincidence techniques have been used to study the ionic fragmentation following excitation and ionization of a sulphur 2p electron in SF₆. This experiment was performed at the FOM Institute for Atomic and Molecular Physics in Amsterdam. An attempt has been made to evaluate alternate theoretical descriptions of certain characteristic inner-shell excitation features in the light of both the electron-ion coincidence results and ISEELS studies of the chloromethanes and SF₆. / Science, Faculty of / Chemistry, Department of / Graduate

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Graduation date: 1991